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Students went back to class at Sandra Day O'Connor High School for the first time since a 15-year-old student shot and killed one of his classmates after school Friday.

Officers were seen collecting evidence Tuesday at the north Phoenix home where they say Matthew Bolton, 15, shot and killed Anastasia Greer, 16, before turning the gun on himself.

According to police, Matthew and Anastasia had recently been through a breakup, but Anastasia's mother, Diannah Dinsmoor, painted a different picture.

"They never went on a date. They never did anything like that. I wouldn't allow it," Dinsmoor said. "She wasn't allowed to date. She only turned 16."

Sources told CBS 5 News Matthew had issues with other students at school and he was suspended for choking a classmate. On Friday, school officials learned of a rumor that a student, possibly Matthew, was carrying a gun on campus. Principal Lynn Miller addressed those rumors in a letter sent home to parents Monday:

Dear Eagle Family,

This is your principal Dr. Miller with information I am truly saddened to communicate with you today.

On Friday afternoon, the school administration was informed that two of our students were identified as the individuals involved in a off campus shooting by the Phoenix Police Department.

We have been working with the police department as they continue this ongoing investigation. There were reported rumors that a firearm may have been on campus. We worked closely with our School Safety Officer and conducted a thorough investigation. The outcome of the investigation did not warrant any validity to the rumors or reason to take additional actions.

We can assure you that school administration takes every inquiry seriously and investigates each matter accurately. At no time was the safety or well-being of your student ever in question.

We know the loss of these students have impacted the lives of many on campus and in the community. Our counselors and district crisis team have been available throughout the day and will continue to meet the needs of our students and staff.

We truly appreciate the support of our school community and will continue to always put students' needs and safety first and foremost.

Although the school claims it could not verify the rumors of a gun on campus, school officials said they were looking for Matthew before early dismissal. According to a district representative, Matthew's parents said he was home with his brother.

"I want to know why [school administrators] had the opportunity to stop this and they didn't," Dinsmoor said. "I want to know why they had this information and they ignored it."

A representative with the school district told CBS 5 News to forward any questions about the murder-suicide to police, who consider this an "open investigation."

Many students were hesitant to say anything about the rumors they heard in class Friday but said they knew Matthew had "talked about violence a lot."

Dinsmoor said she believes this could've been prevented.

"[Ana] was a really amazing gift, I'm really lucky to have had her," Dinsmoor said. "What I want more than anything else is for everybody to give their kid a hug and let them know you love them."

For more on this story and other stories around Arizona from this author, follow Shawn Kline on Facebook and Twitter.

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